Nanostructures Departement

MTA EK MFA Budapest

Click here to receive EMail notification about new uploads to these pages

New Results
Research Topics
Research Equipment
Computational Techniques
Media Coverage
Magyar oldalak HU

Three body problem in three layer graphene
Three body problem in three layer graphene

When an electronic wave packet is propagating in rhombohedral three-layer graphene, it hops between the layers (shown by different colors) in an aperiodic fashion in certain energies. The hopping dynamics of this quantum mechanical system is similar to a simple classical system, three coupled pendulums. Such aperiodic behavior is typical of a 3-body system . This massive wave packet dynamical calculation, including many thousands of atoms, was made possible by our new Carbon pseudopotential.

Publication >>
Video talk about the pseudopotential >>
Video talk about the wave packet dynamical calculation >>
How does a hole influence electronic conduction of a bilayer graphene nanoribbon?
Hole in a BGNR Hole in a BGNR

Wave packet dynamics makes us possible to calculate the transport of electrons in nanosystems containing several thousands of atoms. Figure (a) shows the atomic structure of a bilayer graphene nanoribbon, where the two layers are connected along the cicumference of a hole. Figure (b) and (c) show two electrode configarations used in our calculations. We found that the hole is a kind of energy filter, by changing the voltage applied across the electrodes, it is possible to control the transmission, delay, and reflection of the wave packet.

Publication >>
Reproducible phenotype alteration due to cooling of the pupae of butterflies
Butterfly cooling

Understanding the causal links between the genotype of an organism, the environmental factors, and its phenotype is a hot topic in current biology. We investigated in detail, how an environmental factor (prolonged cooling of the pupae) influence the wing structure of the adult butterflies. This graph shows, that a relatively short cooling (up to 2 weeks) does not influence the eclosed fraction, but somewhat increases the number of wing defets. A prolonged cooling (more that 10 weeks), however, decreases the eclosed fraction to zero. Good illumination during pupation is also an essential factor (see the point marked "low light").

Publication >>
First- and second order light scattering processes in biological photonic nanostructures
First and second order scattering

The image shows a real space lattice of four translation periodic layers with lateral periodicity d and layer distance a. The arrows show the possible light scattering processes -- green is the incoming light, red is the outgoing light. The first- and second order processes (left and right, respectively) give spectral peaks at different locations. In this work we showed that for butterfly wings the visible part of the spectum is generally well reproduced by taking into account first order scattering only, but the second order contribution is important at the UV range.

Vapour sensing properties of graphene-covered gold nanoparticles
graphene on Au vapor sensing

We investigated the vapour sensing properties of different graphene-gold hybrid nanostructures. We observed the shifts in the optical spectra near the local surface plasmon resonance of the gold nanoparticles by changing the concentration and nature of the analytes (ethanol, 2-propanol, and toluene). The smaller, dome-like gold nanoparticles proved to be more sensitive to these vapours compared to slightly larger, flat nanoparticles. We investigated how the optical response of the gold nanoparticles can be tuned with a corrugated graphene overlayer. We showed that the presence of rippled graphene increased the sensitivity to ethanol and 2-propanol, while it decreased it towards toluene exposure (at concentrations higher than 30%). The slope changes observed on the optical response curves were well described by capillary condensation. These results can have potential impact on the development of sensors based on graphene gold nanohybrids.

Dynamic strain in gold nanoparticle supported graphene induced by focused laser irradiation
graphene on Au Graphene on noble-metal nanostructures constitutes an attractive nanocomposite with possible applications in sensors or energy conversion. In this work we study the properties of hybrid graphene/gold nanoparticle structures by Raman spectroscopy and scanning probe methods. The nanoparticles (NPs) were prepared by local annealing of gold thin films using a focused laser beam. Graphene grown by chemical vapour deposition was transferred onto the prepared, closely spaced gold NPs. We found that laser irradiation (and the associated high temperature) induced a dynamic hydrostatic strain in graphene on Au NPs, which turned out to be completely reversible. These results can have implications in enhancing the sensing properties of graphene/plasmonic nanoparticle hybrids using strained graphene in high temperature regime. .
Simulation of vapor dependent spectra of butterfly wings
Albulina metallica TEM and model The reflection spectrum of butterfly wings shows small, but selective changes when subjected to vapors of different liquids. We measued and modeled this phenomenon on such an exceptional butterfly species, Albulina metallica, where the colors of both the upper and lower wing surfaces are physical colors, i.e. given by photonic nanoarchitectures. Figure (a) shows a cross sectional transmission electron micrograph (TEM) of a wing scale of a male Albulina metallica. The dark areas are chitin and the light holes are air voids in the chitin. Figure (b) is the model structure we used in our calculation. Measured and calculated spectra match well. .

Publication -- measurement >>
Publication -- simulation >>
Video abstract (EN) >> Video abstract (HU) >>
Three-state graphene transistor for electronics and spintronics
Three state MoS2 transistor

This image shows the three states of a graphene transistor made of a graphene nanoribbon. According to our theoretical calculations, this transistor has three separate magnetic states, tunable merely with a back gate electrode, without the need of ferromagnetic contacts. This device can serve as a basic building block of hybrid electronic and spintronic graphene data processing systems.

Publication >>
Changes in structural and pigmentary colours in response to cold stress in butterflies
Butterfly cooling

During the past decade, the color patterns of insects have emerged as model systems for studying the interplay between development and evolution. The complex patterns encountered on butterfly wings are more often generated by various pigments than by structural colors, but composite patterns, having both pigmentary and structural origins, also occur. The structural colors of butterflies, generated by sophisticated nanoarchitectures that are able to manipulate light propagation, are frequently used in sexual communication and may be an indicator of mate quality. While numerous papers have investigated the effects of thermal stress on the pigmentary colors of butterfly wings, such studies regarding structural colors are mostly lacking, despite the important role they play in sexual communication. To gain insight into the possible differences between the responses of the two kinds of coloration, we investigated the effects of prolonged cold stress (cooling at 5 C for up to 62 days) on the pupae of Polyommatus icarus butterflies. The wing surfaces colored by photonic crystal-type nanoarchitectures (dorsal) and by pigments (ventral) showed markedly different behaviors.

Publication >>
Graphene covered gold nanoparticles
Graphene on Au

The AFM image shows a graphene/metal nanoparticle hybrid material fabricated by transferring graphene onto closely spaced gold nanoparticles produced on a silica wafer. Graphene is highly rippled and suspended between nanoparticles. This study shows that the graphene Raman peaks are enhanced by a factor which depends on the excitation wavelength, in accordance with the surface plasmon resonance of the gold nanoparticles, and also on the graphene nanoparticle distance which is tuned by annealing at moderate temperatures. Scanning tunneling microscopy and spectroscopy (STM/STS) measurements show that the local density of electronic states in graphene is modulated by the underlying gold nanoparticles.

Publication >>
Bilayered graphene superlattices
Bilayered graphene superlattice

Large scale ab-initio calculations of our Russian partners within the framework of the Faemcar EU Project showed that if we make a hole in bilayered graphene, the edges of the two layers bend and stitch together. If we create many hexagonal holes in a periodic arrangement, the resulting structure is similar to a hexagonal array of nanotubes. Our wave packet dynamical transport calculations proved that this superstructure can be metallic or semiconductor, depending on the size and distance of the holes.

Publication >>
Publication >>
Video about an iridescent butterfly
Left wing of this Morpho butterfly seems bright light, right wing seems brown in this image. This otpical effect called iridescence is because the two wings were seen in different angles when making this photo. Iridescence, together with other interesting effects, is demonstrated in this video. Dr. Krisztián Kertész not only made superb photography, but he even composed and performed the music of the video.
Controlling the nanoscale rippling of graphene with SiO2 nanoparticles
Graphene elasticity

This image shows the elasticity of graphene in nano scale. We covered an array of 25 nm diamener SiO2 nanoparticles with a graphene sheet. The membrane parts bridging the nanoparticles are suspended. Then we scanned this suspended part with an AFM tip and found that a larger force causes a larger indentation. Revealing the details of the elastic behavior of graphene on the nanoscale is very important for creating nanomechanical devices.

Publications >>
Why do grain boundaries deteriorate the excellent properties of graphene?
Ordered, serpentine, and disordered grain boundaries

These images show the increasing disorder in a graphene grain boundary (GB). (a) periodic; (b) "serpentine"; (c) disordered structure. We found that the "serpentine" GB (b), though it does not have 1D periodicity and it is not rectilinear, has similar transport properties than the perfect periodic GB (a), while the resistivity of the disordered GB (c) is much higher. Our calculations show that the increased resistivity is due to the many vacancies and 4-coordinated rings, i.e. the discontinuity of the sp2 network.

Publications >>
Electric field-controlled rippling of graphene

This pair of STM images was recorded on the same 195x195 nm area of graphene, but with different voltage. Note that the ripples, which are seen on both images are sharper on the 0.5 V image than on the 0.1 V image. This means that the shape of the graphene membrane can be controlled by the electric field of the STM tip.

Publications >>
Electronic transport through ordered and disordered graphene grain boundaries

This animation (click here for a larger version) shows the simulated formation process of a disordered graphene grain boundary. Such grain boundaries (GBs) are predominant in CVD prepared graphene and considerably alter the transport properties of the samples. We identified two main factors governing the electronic transport through GBs: the misorientation angle of the two adjacent graphene grains and the atomic structure of the GB. Results show a reduced transport for the disordered GBs, primarily attributed to electronic localized states caused by C atoms with only two covalent bonds.

Publications >>
Grain boundaries in graphene grown by chemical vapor deposition

In this article written by L. P. Biró and Ph. Lambin the scientific literature on graphene grain boundaries was reviewed. Generalized conclusions were formulated, helpful for experimentalists in interpreting the results and planning new experiments. Publications >>
A PhD thesis towards carbon nanotechnology
This image shows a graphene nanoribbon of 35 nm width and atomically controlled edge structure. The image is from the PhD dissertation of Peter Nemes-Incze, entitled "Nanostructures based on graphene and functionalized carbon nanotubes". He developed several basic methods of producing and characterizing carbon nanostructures.
PhD thesis of P.N-I, 5.4 Megabyte) >>
Graphene waveguides
Simulation of a graphene waveguideIf graphene is a promising material in many respects, its remarkable properties may be impaired by unavoidable defects. We have undertaken electron wave-packet dynamics calculations in a multigrain self-supported graphene layer. Our results show that a grain boundary may act as a reflector at some energies. When two grain boundaries run parallel to each other, the graphene ribbon confined between them may behave like a channel for the charge carriers. We emphasize therefore the possibility of creating nanoscale electronic waveguides on the graphene surface by a controlled engineering of its grain boundaries.
Publications >>
Video presentation (3 min, 9 M) >>
The role of structural colours as optical signals in species recognition of butterflies
colors of butterflies in 3D color space
This graph shows the positions of individuals belonging to nine blue butterfly species in the 3D color space. This 3D graph helped us to understand, how butterflies recognize each other, in spite of the color of several species seems to be identical for the human eye. These butterflies, however, posses not three, but four kind of photoreceptors, this makes conspecific recognation possible. Their colors are not produced by pigments, but by nanostructures -- hence these are so called structural colors.
Publications >>
Revealing atomic scale steps of graphene by light microscopy
Linearly polarized light microscopy revealed that graphene grown by chemical vapor
deposition (CVD) on a stepped Cu substrate may appear colored. Polarized light microscopy is an inexpensive, fast, and contamination free method to
visualize graphene and to map the step structure of Cu substrates used for large area CVD growth of graphene.
Publications >>
Mapping the electronic properties of individual graphene grain boundaries
Conductivity map over a graphene grain boundary
This false color tunneling conductivity map shows the electronic structure of a graphene grain boundary. The two graphene grains (left and right regions) are separated by a linear grain boundary (middle region). The conductivity of the grain boundary is much lower. Graphene grain boundaries can form p-n-p junctions with sharp interfaces of the nm scale.
Publications >>
Revealing the grain structure of graphene

This false color AFM image shows the surface of graphene grown by chemical vapor deposition. The colors show the orientation of the grains determined by atomic scale images. Publications >>
Color based discrimination of chitin-air nanocomposites in butterfly scales
Dorsal side perpendicular view photographs of nine investigated Polyommatus species. The spectral signatures of the nine species analyzed using an artificial neural network software show that despite the fact that all possess similar nanostructure, the spectral signatures exhibit enough characteristic differences to allow the unambiguous identification of conspecific individuals. Spectral measurements can be used as a fast and cheap way of checking the relationships of butterfly species in a group having common ancestry
Publications >>
Nanopatterning of graphene with crystallographic orientation control
Computed STM image of a graphene nanoribbon with imperfect edges. Note the localized electronic states on the edges. This shows the paramount importance of edge structure on the electronic properties of graphene nanodevices. Our recent review paper written by L. P. Biró and Ph. Lambin gives an up-to-date survey of methods capable of cutting graphene with precise edge control.
Publications >>
Crystallographically selective nanopatterning of graphene on SiO 2
Hexagonal holes of 380 nm diameter etched into graphene layer on an insulating surface. Our new carbothermal etching process makes it possible to produce graphene nanoribbons and Y-junctions with zigzag or armchair edges.
Publications >>
Supplementary Material >>
Colorful beetle as a model In nanoarchitecture research
During a lecture Professor Biró gave in Taiwan, he was shown three identical-looking beetles, but with different colors. Several months later, we revealed a novel intercalated photonic nanoarchitecture composed of a regular multilayer and nanorods perpendicular to the layers in the elytra of this Taiwanese beetle (Trigonophorus rothschilid varians). We succeeded in producing artificial bioinspired nanoarchitectures, with behaviors very similar to that of the living model, by nanomachining. Our results were published in the journal Interface of the Royal Society, and also displayed on the websites of BBC News and Hungarian Academy of Sciences.
Interface paper >>
News on HAS homepage >>
Biological and bioinspired photonic nanoarchitectures (a video talk)
Photonic nanostructures exhibit a broad range of optical phenomena: coloration, iridescence, photonic band gap, polarization, diffraction, total reflection, fluorescence, etc. These materials have many existing and potential applications in technology, e.g. in communication, signal processing, computing, and as ecological freindly colorants. But biological evolution created photonic nanoarchitectures in living organisms more than 500 Million years ago. This video presentation prepared for Hungarian Physics Students gives and account of our research in this field.
Deltails >>
Role of defects in chemical sensing properties of carbon nanotube films
As the outer wall of the carbon nanotube plays a dominant role in the electrical transport along the axis, the influence of the ambient on its electrical properties offers the possibility of chemical sensing. In our work, the modification of electrical conduction was used as the detection principle in random networks of carbon nanotubes. A sensor made of arc-grown SWCNTs and two others made of arc-grown MWCNTs were also investigated. The response of 24 different sensors to 10 vapors was studied.
AVI movie (5 M) >> Publications >>
Measuring the thickness of graphene layers by TAFM
An Atomic Force Microscope in its "tapping mode" (TAFM) sweeps the sample surface by an oscillating probe attached to a cantilever. This animation shows how does the oscillation change at a step edge and also when the material of the surface is changed below the probe tip. We determined what TAFM imaging parameters are necessary to measure the thickness of thin (< 1 nm) FLG (Few Layer Graphene) layers correctly.
AVI movie (2 M) >> Publications >>
Tailor-made graphene nanoribbons
Results of the Nanostructure Department of the Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences were selected as cover page illustration for the July issue of Nature Nanotechnology (IF: 14.9). According to the Editor, the special importance of the achievements of Tapasztó et al. is that they propose solutions for two major challenges of nanoelectronic circuit manufacturing: the engineered, precise cutting of nanometer size circuit elements and their controlled connecting. A nano-knee ribbon is shown on the cover page of Nature Nanotechnology, two grapheme nanoribbons of only 8 nanometers in width connected with each other under an angle of 30 degreed (the region between the thick red lines).
Publications >>
Bioinspired photonic crystals
Top view Scanning Electron Microscope image of a multilayer structure made from SiO layers and 50 nm Indium spheres (the multilayer was broken to reveal the internal layers). This structure succesfully reproduces the optical properties of Albulina Metallica butterfly wing scales.
Publications >>
Making of graphene layers from oxidation of graphite plates
These 3x3 um Atomic Force Microscopy images show the effect of thermal oxidation on a few-layer graphite platelet (a). We showed that such platelets can be thinned by thermal oxidation in air, and individual graphene layers can be formed (b).
Publications >>
Switchable biological mirror of the tortoise beetle
The tortoise beetle Charidotella egregia is able to modify the structural color of its cuticle reversibly, when disturbed by stressful external events. The gold coloration displayed by animals at rest arises from a chirped multilayer reflector maintained in a perfect coherent state by the presence of special body liquid in the porous patches within each layer, while the red color displayed by disturbed animals results from the destruction of this reflector by the expulsion of the liquid from the porous patches, turning the multilayer into a translucent slab that leaves an unobstructed view of the deeper-lying, pigmented red substrate.
Publications >>
Photonic single- and polycrystal structures on butterfly wings
This image shows the dorsal (a) and ventral (b) surface of the Cyanophrys remus butterfly together with the ventral surface of an old, bleached exemplar (c). With a detailed experimental and theoretical study we showed that while the bright metallic blue dorsal color is caused by photonic single crystal scales, the matt green ventral color is the result of a photonic polycrystal structure. The bleached color (c) is caused by the decay of the absorbing pigment with time.
Publications >> New Scientist >>
Carbon nanotube defects imaged by STM
15x15 nm atomic resolution STM image of a multi-wall carbon nanotube (MWCNT) showing individual atomic-scale defects caused by Ar ion irradiation. The defects appear as hillocks which is due to the increased tunneling current at the defect sites. Electronic superstructures can be observed in the vicinity of the defect sites with the period larger than the period of the atomic structure. (Shown by green lines.) The superstructures appear due to the redistribution of the local density of states (LDOS).
Publications >>
Spray pyrolysis production of CNTs
This 10 um SEM image shows carbon nanotubes produced by the spray pyrolysis method. This method is based on the simultaneous injection of a metallocene-hydrocarbon solution through a sprayer into the reaction furnace. Major advantage of is the direct and continuous generation of fresh catalytic particles throughout the entire growth cycle. This gives the possibility to scale up the method for continuous or semicontinuous production of carbon nanotubes at commercially viable prices.
Details >> Publications >>
BioPhot Symposium 2005
"Complexity and evolution of photonic nanostructures in bioorganism: templates for material sciences", 23. Sept. 2005, Budapest
Details >>
Hungarian Nanotechnology Symposium 2005
HUNS-2005 (MANS-2005) is a national "Mobilization Workshop" organized within the framework of EU FP6 NENAMAT project.
Details >>
Photonic crystals in plants
This SEM image shows the filaments covering the leaflets surrounding Edelweiss (see inset) bracts. The fine structure of the filaments is a photonic crystal structure, one of the few examples of photonic structure found in a plant. Calculations support the idea that this wooly layer absorbs near-UV light before it reaches the cellular tissue.
Publications >>
Wing scale nanostructure in butterflies
Our studies of buttefly wing scale micro- and nanostructure by electron microscopy show that structural color manipulation is a general instrument in the evolution of butterflies. Our study has revealed a deep interwining between physics and biology.
Details >> Publications >>
Biological photonic crystals
This animation shows the variation of the iridescent color of a butterfly as the angle of incident light is changed. This phenomenon is caused by the photonic crystal microstructure of the wing scales. We measure the optical and thermal properties of the wings and study their microstructure by SEM and TEM.
Details >> Publications >>
Coiled nanotubes
A coiled single wall carbon nanotube is shown on this STM image. There are certain catalyst and reaction conditions, which enhance the formation of regularly coiled structures. This may have to do with the formation ratio and the annealing out of pentagon (5) and heptagon (7) rings as compared to hexagons (6). This ratio can be influenced by the proper combination of growth conditions, The annealing out of 5, 7 rings may be avoided by the using of the low reaction temperatures typical for the CVD process, while the high temperatures used in the arc growth anneal out the 5, 7 rings.
Publications >>
An Y-connection of single wall carbon nanotubes is shown on this STM image. Our group was the first to observe SWNT Y-connections predicted earlier theoretically.
Publications >>
Continuous nanotube production in underwater arc

Multi-wall carbon nanotubes are produced by generating an AC electric arc between two identical carbon rods, submerged in deionized water.
Details >> Publications >>
Hexagonal scattering of Bloch waves on a graphene defect
Bloch wave scattering on graphene

Left pane of this animation shows that an electronic wave packet constructed from Bloch waves travels unhindered on a graphene surface. The right pane shows that a structural defect causes scattering to the wave packet. Note that the scatteing pattern is not circular, but hexagonal. Such calculations help us understand the Scanning Tunneling Microscopy images of 2D materials containing structural defects.

Publication >>
Structural color is the same in lowland and mountainous populations of Polyommatus dorylas, despite their size differences
Butterfly generations

This figure shows the generations and photos (male and female) of two different populations of the same butterfly species, Polyommatus dorylas (Turquoise blue). The lowland population (Dorylas, upper row) has two generations each year, but the mountainous population (Magna, lower row) has only one generation (note the winter hybernation of the larvae). As you can see on the photos, Magna exemplars are larger, than Dorylas I and Dorylas II examplars. Our detailed studies showed that the size of the wing scales correlate with the body size, but the dimensions of the photonic nanostructures generating the conspicious blue color remain constant. Hence the optical spectrum is the same for the two populations. This proves that the dimensions of the photonic nanostructure are genetically determined, because the structural color is an important species-specific trait.

Publication >>
Web-Schrödinger 3.2
Diatomic molecule in Web-Schroedinger

Web-Schrödinger is a program for the interactive solution of the time dependent and stationary two dimensional (2D) Schrödinger equation. The program itself runs on our server and can be used through the Internet with a simple Web browser.

The new 3.2 version makes it possible to use piecewise linear and quadratic potentials, as demonstrated on this simple model of a diatomic molecule.

Details >>
Increased catalytic activity in 2D MoS2-xOx crystals
2D MoS2 catalysis

The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single layers, but it also limits their chemical versatility and catalytic activity. The stability of pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption however, L. Tapaszto et. al. recently reported in Nature Chemistry single-atom-level structural investigations that reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. The use of scanning tunnelling microscopy reveals a slow oxygen-substitution reaction, during which individual sulfur atoms are replaced one by one by oxygen, giving rise to solid-solution-type 2D MoS2-xOx crystals. Oxygen substitution sites present all over the basal plane act as single-atom reaction centres, substantially increasing the catalytic activity of the entire MoS2 basal plane for the electrochemical H2 evolution reaction.

Electronic dynamics in graphene and MoS2 systems
MoS2 spreading

This computer simulated image shows a snapshot from the time development of an electronic wave packet injected into the surface of a molybdenum disulfide (MoS2) sheet from the apex of a Scanning Tunneling Microscope tip. Studying the evolution of a packet of electrons having their momentum distributed around a given value gives information on the transport properties of the material. This approach has been used for graphene and MoS2. Due to its complex band structure MoS2 presents an interesting dynamics for electrons.

Publication >>
Biological variability of butterfly colors
Polyammatus isarus and Plebejus argus butterflies

These two butterfly specimens, Polyommatus icarus (A, Common Blue) and Plebejus argus (B, Silver-studded Blue) collected in Hungary (scale bar 10 mm) have similar color to the human eye, but their near UV spectra are different. Despite living in the same type of habitat, these two species display differences in prezygotic mating strategy: the males of P. icarus are patrolling, while P. argus males have sedentary behavior. Therefore, the species-specific photonic nanoarchitecture, which is the source of the structural coloration, may have been subjected to different evolutionary effects. The structural coloration of the four wings of 25 male individuals (100 samples for each species) was measured. Significant differences were found in the near UV wavelength region that are perceptible by these polyommatine butterflies but are invisible to human observers.

Publication >>
Hot pressed nanocarbon-plastic composites for electromagnetic shielding
hot pressed sample

This graph shows the Reflection, Transmission, and Absorption of a 30 um thick nanocarbon-PLA (poly lactic acid) composite as the function of nanocarbon content for 30 GHz microwave radiation. The electromagnetic shielding efficiency increases with increasing amount of nanocarbon in the layer. 3D printing combined with hot pressing is a low cost method to create light-weight and enviromentally friendly electromagnetic shielding layers active in a broad frequency range.

Publication >>
Wave packet dynamics -- different methods for different scenarios
Erwin Schroedinger
Erwin Schr dinger introduced the concept of wave packets in 1926 to bridge the gap between classical and quantum mechanics. The wave packet dynamical method is a scattering experiment inside the computer: an incoming wave packet is "shot" into the physical system and the time development of the packet is calculated. We presented a detailed analysis of different techniques of wave packet dynamical calculations for carbon nanostructures in this book chapter, including Schr dinger equation, Dirac equation, jellium potential, pseudopotential, and multidomain methods.

Publication >>
3D printed nanocarbon sandwich structures
3D printed sandwich

We constructed a new type of light-weight material by 3D printing of nano-carbon doped plastic layers and pure plastic layers -- see the cross sectional optical microscopy image above. Sandwich structures containing only two nanocarbon layers already become not transparent to the microwaves. By such combination of conductive and dielectric materials we can easily realize photonic crystal like structures active in the microwave (GHz) and THz range. These studies serve as a basis for design and realization of optimal geometries of meta-surface type, in order to reach a high level of electromagnetic interference shielding performance for EM cloaking and EM ecology applications.

Publication >>

Room temperature magnetic order on zigzag edges of narrow graphene nanoribbons
2014_10_Nature Experimental data reveal the emergence of magnetic order on edges of sub-10 nm graphene nanoribbons. Using a nanofabrication technique based on Scanning Tunneling Microscopy Lithography, graphene nanoribbons have been fabricated with nanometer precision and edges of well-defined crystallographic orientation. Ribbons with edges of so-called zigzag orientation display a sharp semiconductor-metal transition as a function of their width, which was identified as the signature of a magnetic switching from antiferromagnetic to ferromagnetic coupling between spin-polarized ribbon edges. Remarkably the edge magnetism was found to be stable at room temperature, raising hopes of graphene-based spintronic devices operating under ambient conditions. The results have been published in the October 30th issue of Nature.
The Nature paper >>

Substance specific chemical sensing with butterfly wing scales
Substance specific chemical sensing

This image shows the color change of the butterfly scale in our vapor sensing experiments in the 3D chromaticity diagram using 7 vapors at 10 concentrations. We proved that a modification of the surface may offer a possibility to sensitize / desensitize the sensors for certain volatiles and to produce sensor arrays. Interestingly we found that the evaluation of color changes induced by the different vapors in the 3D visual space of the butterflies ( The role of structural colours as optical signals in species recognition of butterflies) and by Principal Component Analyis (PCA) results in alsmost perfectly coincident trajectories. It is remarkable that a color generating biologic nanoarchitecture, evolved in the scales, and its receptor: the butterfly eye, and a purely matehmatical algorithm yielded the very same result.

Publications >>
"Highlights of 2013" Award
This award certifies that the article Grain boundaries in graphene grown by chemical vapor deposition by L. P. Biró and Ph. Lambin has been selected by the editors of New Journal of Physics for inclusion in the exclusive Highlights of 2013 collection. Papers are chosen on the basis of referee endorsement, novelty, scientific impact and broadness of appeal.
MFA Yearbook 2013
Pages 22-24 and 46-58 of the 2013 Yearbook of the Institute of Technical Physics and Materials Science gives a good overview of the work of our Nanostructures Laboratory, but the whole Yearbook is worth to read, as well as the previous ones!
2013 Yearbook, PDF, 52M >>
Gas sensing with butterfly wings
This animation shows the reversible color change of a butterfly wing when ethanol is dripped on it. Our results showed that a color change also occurs when the wing is exposed to different vapors. This small color change is well measurable in the optical spectrum, the spectrum transition is fast and linear for small concentrations. These features make biological photonic crystals a potential candidate for a cheap gas sensor material.
Publications >>
Bioinspired disordered photonic nanoarchitectures
This image shows a model of a so called 1+2D nanostructure: we deposited a multilayer structure on an array of nanospheres. This bioinspired nanoarchitecture shows peculiar optical properties:  both specular and diffuse reflection.
Publications >>
Color changes upon cooling of butterflies

These images show the different response of butterfly wings upon cooling, depending on whether the color is given by a photonic nanostructure containing open nanovoids or a pigment. The effect is caused by water vapor condensation.

Publications >>
Electronic states of disordered grain boundaries in graphene

This pair of Scanning Tunneling Microscope (STM) images shows an ordered and a disordered grain boundary (GB) in graphene. (Ordered: J.Cervenka et al, disordered: our measurement). Such disordered GBs are often seen in graphene samples prepared by CVD, hence we studied their properties by experimental and theoretical methods. This is important for nanoelectronic applications of graphene.

Publications >>
Selective etching of armchair edges in graphite

Due to its high electron mobility and long coherence length, graphene is a promising material for next generation electronic devices. Patterning graphene with well controlled crystallographic orientation and atomically precise edges is very important for such applications. Formerly, we developed a method for producing graphene edges with zigzag orientation, and our new procedure makes it now possible to etch edges with armchair orientation.

Publications >>
Web-Schrödinger 3.0
Web-Schrödinger is a program for the interactive solution of the time dependent and stationary two dimensional (2D) Schrödinger equation. The program itself runs on our server and can be used through the Internet with a simple Web browser. The stationary states calculation is new in this version 3.0.
Details >> Publications >>
Nanoscale ripples on graphene

L. Tapaszto and coworkers realized subnanometre-wavelength periodic ripples of suspended graphene membranes. The observed nanorippling mode violates the predictions of the continuum model. Nevertheless, microscopic simulations based on a quantum mechanical description of the chemical binding accurately describe the observed rippling mode. The ability of graphene to ripple down to subnanometre wavelengths can be exploited in strain-engineering graphene-based nanoelectronic and nanoelectromechanical devices beyond the boundaries set by continuum mechanics.

Publications >>
Graphene: nanoscale processing and recent applications

This image shows the number of graphene related publications for the years 1990-2011 in logarithmic scale. The fast evolution of research made possible the preparation of samples with arbitrary sizes. Available sample production techniques, combined with the right patterning tools, can be used to tailor the graphene sheet into functional nanostructures, even whole electronic circuits. Our review paper gives a survey of existing graphene patterning techniques and potential applications of related lithographic methods.

Publications >>
Dynamical analysis of the STM tip -- graphene tunneling event
This pair of images shows two situations: when the electron is tunneling from the tip of a Scanning Tunneling Microscope into a bulk sample (left) and when it is tunneling into a thin layer (right), like graphene. In the case of the bulk sample the direction of the momentum of the electron (red arrow) does not change, but for the thin layer the momentum (blue arrow) has to change direction. We analyzed this phenomenon, together with other important effects influencing the STM imaging mechanism of graphene.
Publications >>
Anisotropic dynamics of charge carriers in graphene

This animation (click to enlarge) shows the time evolution of an electron wave packet on the graphene surface. The wave packet is inserted from a simulated Scanning Tunneling Microscope tip (see the left image, a vertical cross section). The right image (horizontal cross section) shows a peculiar anisotropic dynamics, which may have important applications in future graphene nanodevices.

Publications >>
Parallel nanolitography
This STM image shows two graphene nanoribbons etched by a double tip with two apexes situated about 31 nm apart from each other. Parallel processing is of utmost importance if practically relevant nanocircuitry from graphene is targeted. We examined parallel processing of graphene by scanning tunneling lithography (STL) and by carbothermal etching (CTE).
Publications >>
Energy resolved tunneling conductance mapping of functionalized carbon nanotubes
The upper image is a schematic illustration of our novel CNT immobilization technique, which facilitates the study the topography and electronic structure of functionalized CNTs by STM. The technique is based on incorporating the functionalized multiwalled CNTs into a few-layer graphene-nanotube composite, as shown on the lower STM image. Our measurements illustrate the advantage energy resolved tunneling conductance maps can give, namely to spot sample features that are not apparent from STM topography maps and to provide information on local functionalization and doping.
Publications >>
Photonic nanoarchitectures in butterflies and beetles -- a review
Nature began developing photonic nanoarchitectures millions of years before humankind. In their review paper, L. P. Biró and J.-P. Vigneron, present a survey of the development of natural photonic crystal-type nanoarchitectures occurring in butterflies and beetles from the standpoint of physics and materials science The characterization, modeling methods, and rapidly growing number of bioinspired or biomimetic applications are discussed.
Publications >>
Raman scattering on graphene zigzag edges

Theory has predicted rich and very distinct physics for graphene nanodevices with boundaries that follow either the armchair or the zigzag crystallographic directions. We have demonstrated that hexagonal holes obtained by anisotropic etching of graphene are bounded predominantly by zigzag edges which do not contribute to the D peak in Raman spectroscopy.

Publications >>
Graphene by HOPG fluorination and water vapor reduction
STM image (size 3 nm) of the surface of fluorinated graphite in ambient air. Graphite fluoride was obtained by fluorination of highly oriented pyrolytic graphite (HOPG) by a gaseous mixture of BrF3 and Br2. XRD, STM, AFM, Raman spectroscopy and XPS were used to investigate the fluorination process and the reduction of CF2 to graphene on interaction with water vapor. It was found that the crystallinity of the topmost graphene layer produced by reduction is superior as compared to oxidation exfoliated graphene.
Publications >>
Effect of disorder on the color of photonic crystals
This animation shows how the Fourier power spectrum of a perfect crystal is changing, when the lattice planes are randomly shifted. Understanding the effect of randomness on the Fourier image helped us to explain, how the Albulina metallica butterfly creates its viewing angle dependent coloration by a disordered nanostructure.
Publications >>
Tuning the electronic structure of graphene by ion irradiation
We irradiated single atomic layer graphene sheets with Ar+ ions in order to study the effect of defects and disorder on the electronic structure. The samples were investigated by STM and STS. The most important consequence of the induced disorder is the reduction in the Fermi velocity, as illustrated in this figure. Hence we can tune the Fermi velocity of graphene by ion irradiation, which could open up new perspectives for graphene electronics.
Publications >>
Nano Christmas
Wish You Merry Chrsitmas with this nano Christmas tree calculated by Web-Schrödinger. It shows the scattering of a wave packet on a potential forming an X-mas tree. The height of the tree is 3 nm. See the "File / Load Example" menu of the program!
Details >> Publications >>
Photonic nanoarchitectures in butterfly scales as gas sensors
From 20 examined butterfly species all showed selective gas/vapor sensing when various volatile organic compounds were introduced as additives in ambient air. Each butterfly species gives characteristic response both for species, i.e., for its typical nanoarchitecture, and for the seven test vapors used. Fast response time, reproducible and concentration dependent signals are demonstrated.
Publications >>
Diffraction and fluorescence in the iridescence of Troides magellanus
This birdwing butterfly lives in a restricted area of the Philippines. The yellow-green color of its hindwings is caused by a pigment, but as shown on the animation, when viewed at a specific angle, the hindwing shows a bright blue flash. The bright blue color is concentrated at a narrow angular range, this ensures that it is seen only by potential mates, but unseen by the predators. Detailed analysis showed that this effect is caused by a blazed optical grating on the surface of the wing scales.
Publications >>
Interference of electronic waves on the graphite surface
58 x 58 nm atomic resolution STM image of the graphite surface near the vicinity of a defect site created by ion irradiation. Position dependent superstructure patterns are present near the defect, as marked by the two circles. Our results indicate that superstructure patterns are mainly determined by the available scattered states of the system rather than the detailed structure of the defect site. We propose an interference model, which can explain the presence of coexisting superstructures both on graphite and carbon nanotubes.
Publications >>
Transport through a graphene nanoribbon
This animation of 6 fs duration shows the transport of an electronic wave packet through a graphene nanoribbon. Pronounced edge states are seen and the interference of the eigenstates of the nanoribbon causes different patterns to appear along the CC bonds.
Publications >>
BioPhot software & database
BioPhot Analyzer is a program for organized storage and retrieval of images (photographic and microscopic) and measurements of butterfly wing scales. Butterfly specific image- and data analysis tools help the user to understand the raw data. The software was developed by a SME, Softadmin.
Details >>
Imaging electron interference patterns on MWNTs
This animation shows the changing of the calculated STM image of a multi-wall carbon nanotube (MWNT) as a function of the Utip voltage applied to the STM tip. Our new interference model accounts for the complex electron density oscillations near defect sites.
Publications >>
BioPhot Symposium 2007
"Complexity and evolution of photonic nanostructures in bioorganism: templates for material sciences", 24-25. Sept. 2007, Budapest
Details >>
Energetics of CNT bundles
This graph shows the interaction potential curve of two aligned (10,10) carbon nanotubes with one tube fixed and the other rotating about its axis. We studied in detail the energetics of CNT pairs and bundles of CNTs.
Publications >>
Manhattan plot
The statistical distribution of a large number of helically coiled carbon nanotubes was analyzed in a cross-correlated way in their geometrical configuration space defined by diameter and pitch. Stability islands were identified, in which the number of coils exceeds about 15-10 times the value corresponding to a uniform distribution.
Details >> Publications >>
Structural models for coiled nanotubes
By assembling azulene units (fused pentagon-heptagon pairs) and hexagons, and applying specific wrapping rules to these structures resembling some recently-proposed Haeckelite structures (Terrones et al., Phys. Rev. Lett. 84, 1716 (2000)), a large variety of toroidal, coiled, screwlike, and double-helix structurescan be generated. In these structures the ratio of nonhexagonal ringsto hexagonal units varies from 4:1 to 4:3 by contrast to earlier coilmodels where this ratio was well below unity.
Publications >>
3D calculation of tunneling through a SWNT in STM
This is a snapshot from the quantum mechanical time dependent simulation of the tunneling of an electron wave packet through a model of a nanotube in an STM setup.
Details >> Publications >>
2D tunneling calculations through SWNTs in STM
This animation shows the time development of an electron wave packet while tunneling through a model of a nanotube in an STM setup.
Details >> Publications >>

Address: Research Institute for Technical Physics & MaterialsScience H-1525 Budapest , P.O.Box 49, Hungary Tel.: (+36-1) 392-2681, 395-9220 Fax: (+36-1) 392-2226

Last updated: May 9, 2024 by Géza I. Márk ,
This page was accessed  times since Jan 1, 2012.